Recently, the information-communication industry has accomplished a rapid advancement with an increase in demand for the personal computer, the cellular phone, etc. In the fields of electronics and semiconductor, which are led by the information-communication industry, the electronic parts constituting a device become miniaturized and highly integrated, from which necessity for processing technology using laser is increasing, in regards to drilling, cutting, trimming, and scribing of printed circuit boards (PCBs) on which the electronic parts are mounted.
As a processing technology using the laser, for example in Japanese Application Laid Open No. 63-229419 (conventional technology), a lens distortion compensator is disclosed that compensates the inherent distortion of a condensing lens for laser beam, and an example of embodiment for a laser processing equipment using the lens distortion compensator is described. FIG. 11 is a schematic diagram of a laser processing equipment equipped with the lens distortion compensator according to this conventional technology. The lens distortion compensator 107 controls two scanners 102 and 103 for the output from a laser oscillator 101, and the laser processing equipment irradiates the laser beam onto a work piece through a condensing lens 106 by moving two mirrors 104 and 105 that are driven by the scanners 102 and 103. Since the laser processing equipment is equipped with a CCD camera 107 as a condensing point position detection method, while having an X-Y pulse table 108 that can move in the XY direction, a monitor television 110 that displays the optical point position through a camera controller 109 from the output signal of the CCD camera 107 with the scanner position, a table controller 111 that controls the X-Y pulse table 108, and a digital operation processing device 112 that can memorize and compensate the amount of movements of the X-Y pulse table 108, it can calculate the compensation coefficient using a single polynomial model beforehand for every lens, memorize the compensation coefficient, and when using the same lens, reads out a corresponding compensation coefficient to compensate the drive signals for X and Y signals.
However, since the conventional technology only corrects the irradiation position of the laser beam by compensating the lens distortion of a condensing lens without taking the size of a work piece and the time variation of status of the laser processing equipment etc. into consideration, it has a problem that the position accuracy of a processing hole deteriorates depending on the size of processing area, working hours, etc.
Besides, optical systems other than the condensing lens become complicated when the equipment is formed into a multi-beam system for example, in order to enhance workability. However, since the compensation that only works with distortion of a condensing lens is performed, it lacks of flexibility and extendibility that can respond to the complexity.
Furthermore, in the case of the conventional technology, since the single polynomial is used as a model, the model error exists between the single polynomial model with fixed coefficients of a polynomial and the actual system, resulting in a limit in the positioning accuracy of the laser beam.
When using a polynomial model, determination of the degree of the polynomial model is made depending how nonlinear the characteristic of the system of interest is and how good the approximation accuracy should be. In general, although the approximation accuracy becomes good when raising the degree of a polynomial, a problem is that the necessary calibration points increase or the calculation time of command values that controls the irradiation position of a laser beam increases, resulting in a decline of workability.
It is an object of the present invention, therefore, to achieve a laser processing equipment that reduces errors caused by model errors between the conventional polynomial model and the real system, suppresses any increase in calibration time and calculation time even when the approximation accuracy of the polynomial model is raised, and maintains the processing accuracy even against various changing factors, such as the size of work piece, time variation of status of the system, etc.